U.S. patent number 6,814,037 [Application Number 10/602,993] was granted by the patent office on 2004-11-09 for variable camshaft timing for internal combustion engine with actuator locking.
This patent grant is currently assigned to BorgWarner Inc.. Invention is credited to Michael Duffield, Marty Gardner, Roger Simpson, Franklin R. Smith, Braman Wing.
United States Patent |
6,814,037 |
Smith , et al. |
November 9, 2004 |
Variable camshaft timing for internal combustion engine with
actuator locking
Abstract
A variable camshaft timing system having a camshaft with a
vane-type rotor, where oscillation of the housing relative to the
vane is actuated by pressurized engine oil, derived in part from a
torque pulse in the camshaft. An annular locking plate is
positioned coaxially with the camshaft and the housing. It is
moveable relative to the housing along the longitudinal central
axis of the camshaft between two positions, the teeth on the
locking plate engaging the teeth on the housing and where the teeth
on the locking plate are disengaged from the teeth on the housing,
each position preventing circumferential movement of the housing
relative to the rotor. The locking plate is biased by a plurality
of metallic straps towards engagement of the teeth on locking plate
with the teeth on the housing. The straps have one end secured to
the locking plate and another end secured to the rotor.
Inventors: |
Smith; Franklin R. (Cortland,
NY), Simpson; Roger (Ithaca, NY), Gardner; Marty
(Ithaca, NY), Wing; Braman (Interlaken, NY), Duffield;
Michael (Medina, NY) |
Assignee: |
BorgWarner Inc. (Auburn Hills,
MI)
|
Family
ID: |
33311059 |
Appl.
No.: |
10/602,993 |
Filed: |
June 24, 2003 |
Current U.S.
Class: |
123/90.17;
123/90.15; 74/568R |
Current CPC
Class: |
F01L
1/022 (20130101); F01L 1/34409 (20130101); F01L
1/3442 (20130101); F01L 2001/34426 (20130101); Y10T
74/2102 (20150115); F01L 2001/34433 (20130101); F01L
2001/34453 (20130101); F01L 2001/34459 (20130101); F01L
2001/3443 (20130101) |
Current International
Class: |
F01L
1/344 (20060101); F01L 001/34 () |
Field of
Search: |
;123/90.12,90.15,90.16,90.17,90.18 ;74/568R ;464/1,2,160 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Denion; Thomas
Assistant Examiner: Corrigan; Jaime
Attorney, Agent or Firm: Brown & Michaels, PC
Dziegielewski; Greg
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is directed to improvements of the invention that
is described and claimed in U.S. Pat. No. 6,250,265, which issued
on Jun. 26, 2001, the disclosure of which is incorporated by
reference herein.
Claims
What is claimed is:
1. A variable camshaft timing device for an internal combustion
engine having at least one camshaft comprising: a vane-type rotor
having at least one lobe secured to the camshaft for rotation
therewith, the rotor being non-oscillatable with respect to the
camshaft; an annular housing surrounding the rotor and having a
first annular array of teeth and at least one recess having a
circumferential extent greater than the circumferential extent of
the at least one lobe and receiving the at least one lobe, the
annular housing being rotatable with the camshaft and the rotor,
and being oscillatable with respect to the camshaft and the rotor;
a locking means reactive to engine oil pressure for preventing
relative circumferential motion between the housing and the rotor
at one of a plurality of relative circumferential position of the
housing and the rotor during periods of low engine oil pressure,
the locking means comprising an annular locking plate having a
second annular array of teeth in engagement with the first annular
array of teeth in a first position of the annular locking plate to
prevent relative motion between the housing and the rotor and being
out of engagement with the first annular array of teeth in a second
position of the annular locking plate to permit relative
circumferential motion between the annular housing and the rotor,
and at least one metallic strap having an end secured to the
annular locking plate and an opposed end secured to the rotor for
urging the locking means to the first position in locking
engagement with the rotor during periods of low engine oil
pressure.
2. The variable camshaft timing system of claim 1, wherein the
annular locking plate is positioned relative to a longitudinal
central axis of the camshaft and is moveable along the longitudinal
central axis of the camshaft between the first position and the
second position.
3. The variable camshaft timing system of claim 2, wherein the at
least one metallic strap comprises at least three circumferentially
spaced apart metallic straps, each of the metallic straps having an
end secured to the locking plate and an opposed end secured to the
rotor.
4. The variable camshaft timing system of claim 1, wherein the
rotor comprises at least three circumferentially spaced apart
vanes, and wherein the annular housing comprises a like number of
circumferentially spaced apart recesses.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a variable valve timing system for an
internal combustion engine. More particularly, this invention
relates to a torque pulse actuated, hydraulic variable valve timing
system of the foregoing type with locking capabilities to lock the
components of the system in a fixed condition of operation during
intervals of low hydraulic pressure, such as during engine
start-up.
DESCRIPTION OF RELATED ART
U.S. Pat. No. 5,107,804 (Becker et al.), which is assigned to the
assignee of this application, the disclosure of which is
incorporated by reference herein, describes a vane-type, camshaft
torque pulse actuated hydraulic camshaft or valve timing system for
an internal combustion engine in which the hydraulic fluid that
operates the camshaft phase shifting system is engine oil. Such a
system has many operating advantages over other known types of
valve or camshaft timing systems, for example, in the timeliness of
response to changes in engine operating conditions. However, such
systems tend to be noisy or otherwise unstable during periods of
low engine oil pressure, which can often occur during engine
start-up and can occasionally occur during other types of operating
conditions. During these times, it is important to be able to lock
the otherwise relatively movable components of the system into
fixed positions relative to one another, and it is to the provision
of an improved solution of the system locking requirements of such
a variable valve timing system that the present invention is
directed.
U.S. Pat. No. 2,861,557 (Stolte) also describes a hydraulic
variable camshaft timing system, albeit a system that is operated
solely by engine oil pressure. This reference teaches that it is
desirable to lock the otherwise variable components of the system
in fixed positions relative to one another during low speed
operation conditions, but only teaches a system in which a single
set of fixed positions can be achieved.
The invention of the aforesaid U.S. Pat. No. 6,250,265 is a
hydraulic variable camshaft timing system with a locking plate that
is spring biased against engine oil pressure from a position out of
locking engagement with a variable position camshaft phaser housing
when engine oil pressure is high, and into a locking position with
the phaser housing when engine oil pressure is low. The locking
plate of this invention has a multitude of teeth in an annular
array, and the teeth of the locking plate engage the teeth of the
phaser housing when the locking plate is in locking engagement with
the phaser housing. Because the locking plate and the phaser
housing each have a multitude of engageable teeth, the locking
plate can lockingly engage the phaser housing at a multitude of
relative circumferential positions between the locking plate and
the phaser housing. The ability of the invention of U.S. Pat. No.
6,250,265 to lock the phaser housing in any of a multitude of
relative positions beneficially reduces phaser oil consumption and
phaser oscillation or dither, and it reduces the control system
operating requirements from fulltime, in a system where there is no
locking capability, to part-time.
It is known in the art that any camshaft phaser locking arrangement
must be torsionally rigid, but axially flexible, to reliably engage
and disengage when required. It must also be able to operate with
minimal backlash between the locking plate and the phaser
housing.
SUMMARY OF THE INVENTION
A variable camshaft timing system according to the present
invention is, like the system of the aforesaid U.S. Pat. No.
6,250,265, a camshaft torque pulse actuated, engine oil powered
hydraulic system that is used to change the position of a lobed
vane-type rotor within lobe receiving recesses of a surrounding
housing. Further, the variable camshaft timing system of the
present invention, like that of the aforesaid U.S. Pat. No.
6,250,265, has a locking plate that is spring biased against the
effects of engine oil pressure, to prevent relative motion between
the rotor and the housing, except when the engine oil pressure
exceeds a predetermined value, and locking according to the present
invention, like that of the aforesaid U.S. Pat. No. 6,250,265, can
occur at one or another of a multitude of positions of the rotor
and the housing relative to one another. It is also contemplated
that the invention of the present application can be adapted to an
hybrid variable camshaft timing system operated both on engine oil
pressure and oil pressure resulting from camshaft torque pulses,
such as that of U.S. Pat. No. 5,657,725 (Butterfield et al.), which
is also assigned to the assignee of this application, the
disclosure of which is also incorporated by reference herein, and
to an engine oil pressure activated system such as that of the
aforesaid U.S. Pat. No. 2,861,557.
Unlike the invention of the aforesaid U.S. Pat. No. 6,250,265
however, the locking plate of the present invention is physically
connected to the lobed rotor of the variable camshaft timing
phaser, and this connection is by way of a plurality of straps,
preferably three straps, which are arranged in an annular array,
opposed ends of each of which are secured, for example, by riveting
or bolting, to the locking plate and the lobed rotor, respectively.
The straps are oriented so that, in their non-locking positions of
the locking plate and the rotor of the phaser, they serve to bias
the locking plate toward the rotor against the effects of engine
oil pressure acting on the locking plate. Thus, when the engine oil
pressure falls below an acceptable minimum, an on/off solenoid,
which controls the oil pressure, turns off, and the straps bias the
locking plate into locking position with the rotor of the
phaser.
The strap connection between the locking plate and the rotor of the
phaser is axially flexible, in that it permits rapid engagement and
disengagement between such elements and it is also
circumferentially rigid, to thereby prevent relative
circumferential motion therebetween. Further, the strap connection
between the locking plate and the phaser rotor makes it possible to
eliminate or to substantially eliminate backlash between the
locking plate and the rotor, compared to that achieved by the
invention of U.S. Pat. No. 6,250,265, by providing wedge-shaped
interengaging teeth on the locking plate and the rotor. This form
of engagement is a very low backlash form of engagement in
comparison to engagement by interengaging spline teeth.
Accordingly, it is an object of the present invention to provide an
improved vane-type, torque pulse actuated, hydraulic variable valve
timing, or variable camshaft timing system for an internal
combustion engine. More particularly, it is an object of the
present invention to provide a variable valve timing or variable
camshaft timing system of the foregoing character, with an improved
arrangement for locking a position of a lobed rotor relative to the
position of the housing, in which the rotor is normally free to
oscillate whenever engine operating conditions make it desirable to
prevent relative motion between the rotor and the housing. Even
more particularly, it is an object of the present invention to
provide a variable valve timing or a variable camshaft timing
system of the foregoing character that eliminates or virtually
eliminates backlash between a locking plate of the system and the
rotor thereof.
For a further understanding of the present invention and the
objects thereof, attention is directed to the drawings and the
following brief description thereof, to the detailed description of
the preferred embodiment and to the appended claims.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1A and 1B show an exploded perspective view of the elements
of a variable camshaft timing system according to the preferred
embodiment of the present invention.
FIG. 2 shows an end elevational view of a variable camshaft timing
system according to FIGS. 1A and 1B.
FIG. 3 shows a sectional view taken along line 3--3 of FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
A variable camshaft timing system according to the present
invention is provided with a vane-type rotor 10, the rotor 10 being
provided with a plurality of radially outwardly projecting lobes,
shown as three (3) such lobes 12, 14, 16. An annular sprocket-type
housing 18 surrounds the rotor 10, and the housing 18 has recesses
20, 22, 24, which receive the lobes 12, 14, 16, respectively. The
rotor 10 is bolted to a flange 46a at an end of an extension 46 to
a rotating camshaft 26 with an inner plate 28 positioned
therebetween, so that the rotor 10 is rotatable with the camshaft
26, but is not oscillatable with respect thereto. The housing 18 is
provided with sprocket teeth 30 on an exterior thereof. The
assembly that includes the camshaft 26, with the rotor 10 and the
housing 18, is caused to rotate by torque applied to the housing 18
by an endless chain (not shown) that engages the sprocket teeth 30,
and motion is imparted to the endless chain by a rotating
crankshaft (not shown) or another rotating camshaft (also not
shown). However, the housing 18, which rotates with the camshaft
26, as explained, is oscillatable with respect to the camshaft 26
to change the phase of the camshaft 26 relative to the crankshaft
or to another camshaft. In that regard, the circumferential extent
of each of the recesses 20, 22, 24 is greater than the
circumferential extent of each of the lobes 12, 14, 16 that is
received therein to permit limited relative circumferential motion
between the housing 18 and the rotor 10. To enclose the recesses
20, 22, 24 of the housing 18, a cover plate 32 is bolted to the
rotor 10 by a plurality of circumferentially spaced apart bolts 34,
and an annular seal 36, which is positioned in a recess 38 on an
outer face of the housing 18 to sealingly engage a face of the
cover plate 32.
Makeup engine oil from an engine main oil gallery (not shown) flows
into the recesses 20, 22, 24 by way of a passage 44 in the camshaft
bearing extension 46, the oil being selectively distributed to one
side or the other of the lobes 12, 14, 16 in the recesses 20, 22,
24 by a sliding action of a spool valve 48 that is positioned
within the rotor 10 and cover plate 32 coaxially of the camshaft 26
and the camshaft extension 46, as is explained in the aforesaid
U.S. Pat. No. 5,107,804.
An annular locking plate 50 is positioned concentrically with
respect to the rotor 10 and the cover plate 32, and is axially
slidable with respect to the rotor 10 and the cover plate 32. The
locking plate 50 is provided with a plurality of teeth 52 in an
annular array, and the teeth 52 are positioned to engage a
plurality of teeth 54 on the housing 18 when the locking plate 50
is at an axially innermost position relative to the housing 18,
which prevents relative oscillating motion between the housing 18
and the rotor 10. However, at an axially outermost position of the
locking plate 50, the teeth 52 are out of engagement with the teeth
54, to permit relative oscillating motion between the housing 18
and the rotor 10. The locking plate 50 is urged to such an axially
outer most position by the pressure of the engine oil from an
independent passage 96, located in the camshaft bearing extension
46. The oil present in the passage 96 is controlled by an on/off
solenoid 90. Depending on the state of the on/off solenoid, the
locking plate is urged to an axially outermost position on a
locking piston 56, which is sealingly positioned relative to the
locking plate 50 within an annulus of the locking plate 50 to
axially reciprocate with the locking plate 50. An annular seal 58
is positioned in a recess 60 on an outside diameter of the locking
piston 56 to permit relative axial motion between the locking
piston 56 and an inside diameter of the cover plate 32, and a
C-shaped retaining ring 62 is positioned in a recess 64 of an
inside diameter of the cover plate 32 to prevent excessive outward
motion of the locking piston 56 relative to the cover plate 32.
The locking plate 50 is spring biased to its axially innermost
position by a plurality of metallic straps 70, shown as three (3)
such straps. In that regard, each of the straps 70 is flat in its
rest or unloaded position, and is distorted in a nearly Z-shaped
configuration in the unlocking position of the locking plate 50. An
end 70a of each of the straps 70 is secured to the locking plate 50
by a rivet 72, and an opposed end 70b of each of the straps 70 is
secured to the cover plate 32 by a threaded fastener 74 with a
washer 76 being provided therefor. The locking plate 50 is provided
with a plurality of apertures 78 that are axially aligned with a
threaded fastener 74, but somewhat larger than the threaded
fastener 74, to permit relative axial motion between the locking
plate 50 and the cover plate 32. The use of a riveted connection
between the end 70b of each of the straps 70 and the cover plate 32
is also contemplated.
The engagement between the teeth 52 on the locking plate 50 and the
teeth 54 on the housing 18 can be essentially free of backlash if a
wedge shape is provided for each of such teeth, whereas an
engagement between interengaging splined teeth between elements
that move axially relative to each other must inherently have some
backlash between such elements. In that regard, it has been found
that an angle of five degrees on each of the wedge-shaped teeth 52,
54 provides for good torque transmission with a minimum amount of
engagement and virtually no backlash. A tapered tooth angle on
wedge-shaped teeth provides increased torque transmission, but
involves some minimal backlash to avoid wedging of the locking
plate 50 into the annular housing 18. Further, the use of a large
number of teeth 52 to engage a like number of teeth 54 avoids the
need to ensure that the locking plate 50 and the annular housing 18
are closely circumferentially aligned before the locking plate 50
can engage the annular housing 18. To minimize loads on the teeth
52, 54 when they are engaged, it is preferable that they be
positioned on large, external diameters. This will also allow the
use of finer pitch teeth and more locking positions.
The camshaft bearing extension 46 is rotatably supported in a split
bearing that is made up of a lower half 80 and an upper half 82,
which are removably joined to each other by threaded fasteners 84.
The bearing formed by the bearing halves 80, 82 also functions as a
valve to introduce engine oil through a radial passage 86 in the
camshaft extension bearing 46. Three independent passages,
including the radial passage 86 are present in the camshaft
extension bearing 46 and allow the flow of engine oil into the VCT
system. The first independent passage 44 is the passage for engine
oil supplied to fill the phaser and to make up the oil that is lost
through leakage. The second passage 86 is controlled via a
pulse-width modulated (PWM) solenoid 88. The PWM solenoid 88
modulates the pressure that moves the spool valve 48, which
controls the direction of the VCT actuation and the rate of change
of the actuation. The third independent passage 96 communicates
with the locking plate and is controlled by the on/off solenoid 90.
The on/off solenoid 90 controls when the locking plate 50 engages
and disengages the rotor 10. The on/off solenoid 90 is secured to
the upper half 82 of the bearing by a mounting bracket 92.
The variable camshaft timing system of the present invention, as
heretofore described, can be controlled in its operation either by
an open loop control system or a closed loop control system, both
of which are described in the aforesaid Ser. No. 09/450,456.
Further, because the locking plate 50 of the VCT system of the
present invention is external to the other elements of the system,
it is adaptable to other types of VCT systems, such as engine oil
pressure actuated systems, for example, of the type described in
co-pending U.S. patent application Ser. No. 09/473,804, which is
assigned to the assignee of the present application, the disclosure
of which is also incorporated by reference herein, and hybrid
systems, such as those described in the aforesaid U.S. Pat. No.
5,657,725.
Accordingly, it is to be understood that the embodiments of the
invention herein described are merely illustrative of the
application of the principles of the invention. Reference herein to
details of the illustrated embodiments is not intended to limit the
scope of the claims, which themselves recite those features
regarded as essential to the invention.
* * * * *